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okay, let's begin, let's begin. what are we gonna talk about today? - relativity. - yay, all right. we saw the film. relativistic time dilation, okay? steve smith did all the drawings. i told you steve smith was a dishwasher and after submitting the film to the american educational film festival in 1977 that got him first prize. steve then advanced to the status of a taxi driver. yeah, yeah, the arts, the arts. very rewarding, gang. why is it mommy and daddy get disappointed when you say you wanna be an art major, right? with the prices of housing going up, you say, you wanna be an art major, huh? on the film, we saw where time seemed to be different for people traveling and time was different for people at rest.
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it turned out the speed of travel for that particular case where we go from 2 hours to 2 1/2 hours was 60% the speed of light. you saw the film that kinda got into all the stuff about counting flashes, counting flashes and all that sort of things. would you like to see that nice and succinct so there's no question? so when you look at what i'm gonna put on the board, boom, it all makes sense? time dilation comes alive. would you like to see that? i can do that for you right on that empty part of the board. would you like to see it? never mind the talk, never mind the rhetoric. let's get to it, huh?. here's time dilation. hey-ey-ey. all right, huh? - that do it for you? - yeah. now...what's that mean? this is derived in the footnote of your textbook,
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is that not true? simple pythagorean theorem, right? geometry, okay? i won't go through the elaboration now. but it just states that the time, the funny business, time. the time that one will experience due to relativistic effects-- meaning really motion effects, huh? the time that one will experience will have to do with the time that one would experience if there were no motion at all. t sub zero. but modified by the square root of 1 minus v-squared/c-squared v is the relative speed between that being observed and that observing. that's important, very important. this v, to understand what that means. the nature of what that v is, is at the root of a lot of misconceptions about relativity. again, v stands for the velocity between the observed and the observer. let me give you an example.
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if i put numbers in like this, 87% the speed of light, i put in there 0.87c and do that, it turns out my time will be twice. i'll observe things take twice as long a time, okay? now let's suppose, i travel relative to you guys at 87% the speed of light. and if you guys watch my watch undergo its second-hand thing, you guys will see my watch taking twice as long to make one complete turn. you hear what i'm saying? you'll see it stretched out by 2. now travel with me. and we'll watch. now we're going at 87% the speed of light, you and i together. you look at my watch. you see any funny business? what's v? - zero - zero. because the observed, the watch. the observer, there is no relative speed between the observer and the observed. get it? so you in the rocket ship notice nothing unusual if you travel along with the watch.
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then v is zero in this equation. and if v is zero, then this term is zero. what's 1 take away zero? 1. what's the square root of 1? 1. and how do your times compare? there's no difference. my time, your time, same same, okay? so that's very important to understand what that v is. now in our particular case, v for this example was 60% the speed of light. let's see what happens when we put that in there. if it was a 2-hour trip with no funny business.
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now 6 x 6, 0.36, and c-squared and c-squared, cancel out. so it's 1 minus 0.36. does anyone know what that is? okay, it's going to be 64. 1 minus that it's gonna be 0.64. but now you gotta know the square root of 0.64. you know the square root of 64, 8 x 8 = 64. what about 0.64? it's 0.8. now you gotta know how many times does .08 go into 2. calculator types? well, i'll tell you, i've done it before. 2.5. yeah, 0.8 will go into 2, 2.5 times. so you know what? the time that the earth types see
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is the 2 hours that they would see if their velocity were zero. t sub zero. the time that the earth types see is that 2 hours but modified by this thing over here and it's called the lorentz fitzgerald contraction factor, all right? and then v is the speed, the relative speed. and c, of course, the speed of light. and we've done that, we find out that, wow, a 2-hour trip appears to be 2 1/2 hours. and that's what we saw in the film. now if you go at higher speeds, the time dilation-- dilation means stretched out. the stretch-out of time is even more. if you went 87% the speed of light, i'm not gonna take the time to do that now. but if i put the 0.87 in here, i would come out over here where the time is twice as much. twice as much time, see? so 2 hours will be 4 hour trip. and if i went 99.5% the speed of light, that fast, then it turns out the time would be 10 times as much.
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so a 2 hour-trip would look like 20 hours. let's take the extreme case. what if i went at the speed of light itself? okay. then this would be just c, not a fraction of c, but c. and c-squared, c-squared, what? is one. what's one take away one, gang? - zero. - zero. what's the square root of zero? - zero. - zero. how many times does zero go into any number? i mean, think of zero as being something tiny, okay? how many times something tiny go into something big? infinite. so it turns out as the speed of light, if something gets up to the speed of light, time becomes like infinite. take an infinite time for that 2 hours to go by. we've talked about this before, time would be frozen. you would see time frozen. so at everyday speeds, how about speeds, like, you, when you walk down the street? does time dilation occur when you walk down the street? i should have asked this in the quiz, yeah?
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does any time dilation occur when you walk down the street and your friend sits on the curb? - a lot or a little? - little. little, but it's happening. some people think that the effects of relativity only occur beyond some particular speed. that's not true. they occur at everyday speeds but the effects are negligible, small enough to be neglected. so i mean, if you put like this, your speed in here put the speed of something moving, okay? how fast does the space shuttle move? maybe like a thousand the speed of light, okay? and even less than that, okay? so you got 0.001 and then square that, you pretty much get the 2 hours. when these astronaut type go up and they go round, round, round, they come back down. they're not even a second different in time, not even 1 second. because their speeds are trivial compared to the speed of light, but it's there. it's only for very, very high speeds that the effect becomes apparent. and those speeds, we don't deal with in the everyday world
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so its not common sense to us. maybe in tomorrow's world, when we goose up to speeds like that, it will be. i'll give you an example. when you go to the travel agents today you see these exotic posters on their walls, right? they get posters of the hawaiian islands, right? and everyone wants to spend a little time in the hawaiian islands, right? so they put these posters of the hawaiian islands with the palm trees and all that, the royal hawaiian hotel and all-- it makes you wanna get a couple of weeks off and go there, doesn't it? anyway, you see these posters of places. how many posters have you ever seen in a travel agent that posts times? like, you can talk about traveling to south america, you can talk about traveling to the mainland. you can talk about traveling to europe, but can you go to the travel agent today and talk about traveling into time? we got new years coming up. we got a big one pretty soon, 2000, the year 2000, okay? and then 2001, 21st century, yeah? how about someone says,
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well, i'm not so much interested in that. i'm kind of a futurist. most of my friends are sort of like historians. they study history, where we've been. and it's kind of a real gas to know where we've been and where we are now. but my bit is where are we going? that's what i'm interested in. and what i'd like to do is i'd like to travel to the 25th century. and i'd like to see what human beings are doing for new year's eve in the year 2500, okay? what's it gonna be like then? now you go to your travel agent now and ask, you know what they're gonna say to you? the same thing they would have said to you a century ago if you told them you wanted to go from one part to the other part of the world in a metal airplane. they'd say, come on, you can't fly, metal's too heavy. but we can fly today. tomorrow, we might be century hopping, my friends, century hopping. you might go into the travel agency and say, hey, i wanna visit the year 2500. and you take that trip.
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but the travel agent says, oh, if you wanna go that far ahead in time, that's gonna take you 3 months, that's a 3-month trip, 'because our rocket, this particular rocket, the alpha rocket will take it 3 months. what are you gonna do for 3 months? and you say, well, i'm going to bring along my reading, all right? and so you'll be properly entertained for 3 months. and you take the 3 months trip. you come back to the earth, maybe it's 2500. can you do that today? can't do it today, don't have the technology. tomorrow, maybe not, maybe so, who knows? these ideas right now are far-fetched. but i'll tell you one thing, when you travel through space, you travel through time. and some people think it's like outer space, like there's something magic about outer space, okay? let's suppose someone said to you, hey, i wonder what it's like in outer space. what is it like in outer space, gang? guess who's there already. we are.
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the earth is in outer space. in control or out of control? completely out of control. and the earth is just hurling through space. any time we could hit a bunch of meteors-- we know what happened to the dinosaurs a few years ago. at any time. i don't want to arouse your paranoia, but the earth is in outer space, it's been in outer space all the time. and we are space creatures, we are in outer space. and some people think that all these ideas of relativity has to do with that space out there. that's not true. you could take the space of this room. a little scenario, let's suppose in this room we had a centrifuge. in that centrifuge whirl around, around, around. and you guys stand outside. and some people in the centrifuge whirling around. is there any speed relative to you for them? yeah, there's a speed, okay, there's a speed. this v in the equation would have some value. let's suppose you got on a centrifuge like that, let's suppose you did something like this. you're in the centrifuge, you're sitting down. they belt you in, okay?
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you're all belted in and this thing is part of the rim right here, it's gonna whirl round, round, round. now what would happen if you sat in a chair like that, belted in? back, of course, your head. you don't want your neck to break. what would happen if they boost it up till you're going like speeds near the speed of light? would you be comfortable or a little bit nauseous? honey, you would be dead, okay? you'd be splattered all over that thing, right? centrifugal force, okay? you wouldn't make it, you wouldn't make it. the acceleration would be too enormous. but let's make believe, let's make believe you could sit in the centrifuge and go up to the speeds near the speed of light without getting killed. just make believe, okay? what might happen? it might go like this, they say to you, okay, here's a little red button down here. when you get tired, for any reason you want us to stop, hit the red button, outside, the alarm will sound and when the alarm sounds, we'll cut down the electricity and that'll bring it down to a stop, open it up and see how you're doing. you are the first one to try this, so good luck. so they go out, they close door, they get you belted in.
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you feel that thing vibrating. you're picking up speed, picking up speed. and you say, gee, this thing's really going, okay? and you say, i did about 10 minutes, i'm getting bored. i'm getting bored, i wanna get out and read my physics book. i left my physics book outside. you hit the red button. outside, alarm, okay? they pull down the switch and electricity stops. door opens up. someone looks in and says, what you've been eating for the last 3 months? how did you go to the bathroom? you've been belted in, what have you been doing? how come you waited so long before you hit the button, man? you see, for you it's a few minutes, but for them, 3 months. this happens with radioactive decay. measure the radioactive decay rate of a mineral. now have the mineral move relative to the counter. the decay rate changes.
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these ideas are solid, gang. some people ask, what would happen if you travel faster than the speed of light, could you do that? as we understand relativity, we say, no, you can't do that. hyperspace and star wars not withstanding. you can't go faster than the speed of light, but what if you could is oftentimes the question. and it turns out to be that if you could, it'd be kind of bizarre. would you like to see what i'm trying to say? let's suppose you did this. let's suppose you're on this planet, the earth. and you wanna jump to another planet. and you're gonna travel between planets at a speed greater than light. now you can't do that. but let's make believe. and let's suppose up in this other planet here, you have a tripod all set up and you can stand there and look through and look right down through the path.
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and here you are down here. you're in front of a great big clock like einstein had in his village square. and what you do is you jump and you say, boom, shazam , okay? all of a sudden you become super-something, okay? and you fly up here. well, here you go on your trip when you jump up. first, you get here, then you're here then you're here and then all of a sudden, you're up here, okay? what would a trip like that be like? let me ask you a question. what would you or who would you see in the telescope? think about that. who would you see? what would you see? if you could go faster than light, faster than light, i know you can't do that, lee. let's make believe, let's make believe. if you could go faster than light and you took a look here, who would you see? the most important person on all the universe, yourself. i'm kidding about that, okay. but you see yourself.
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now would you see yourself like this. shazam. you see yourself getting closer, closer, closer. you're all together. would you see that? answer begins with a 'n'. you see something more weird than that, much more weird. let me give you a hint. first of all, you're here. later on, you get to there. and after that, you get to here. so yes, you would see yourself. but would you see yourself at position 1, then 2, then 3? you're going faster than the light that's bouncing off you. what would it be, gang? check your neighbor and see if your neighbor has any idea what's going on. how are you gonna see yourself? your gonna see 1, 2, 3? how many people say, no, i think you're gonna see 3, 2, 1? let's suppose when you made that jump, you got a watch, you got a great big one, big mickey mouse job, okay?
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and you put it right here, a draping giant one, okay? you seen those ones in the fun shops? and you got that watch and you go up like that. so you can look at the watch that you're wearing on your wrist. let me ask you a question. which way is that watch you're gonna be reading, forward in time or backward in time? backward. - begin with with a what? - b. b, you see that. you're gonna see yourself going back down. you'll see yourself here. and then here and then here. 'cause you got up there faster than light. and so that light didn't like come in toward you. so you see yourself going backward. i got another question for you. when you're looking at the clock in the background, in the background, all the time is the clock with the great big hand. how are you seeing that time going? counterclockwise. regular or backwards. let me ask you guys a question. if you just get out here and look at the telescope and there's no motion between you and this clock down here, are you gonna see that clock just moving as regular?
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how many say, yes? oh, you guys don't know that. well, let me ask you this question here. if you stand on a tower outside and you u got a spyglass and you look at the clock downtown, is that clock gonna do something funny? all right, let's suppose you get another planet and you look at the clock downtown, is it gonna do something funny? how many say, hey, it'll run just like it always runs? well, not everybody. well, let me just tell you, nothing's funny. it's only when you're moving, okay? when you're moving. and so what you'd see here, you see the clock here running backward. and back here, you'd see the clock running forward. so in one eyeball-full, you'd see time going backward and forward. bizarro. lee? now it's the you that's on the planet that's seeing this, there are two yous. there's a you that's flying through space and there's a you that's on the planet. and when i was answering your question first, it seemed to me that if you're looking ahead of you,
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their light wouldn't have reached the telescope before you got to the planet if it's the you that's flying through the space. it's the you that's on the planet that sees the you coming down. lee, you get up here at the telescope before this light gets to you, because you've gone faster than light. you get up here first. you're waiting for the light to get to you. and all we're saying is this light will get to you first because it's closer. and this light will get to you later 'cause it's further away and so on. so you'll really see yourself going backwards in time. now how long will this backward sequence last? could you see yourself going backward? you land, you start walking backwards, you get in your car, you drive back. you keep watching patiently. you see yourself when you're going to college at u.h., remember that? then you see yourself when you were in high school. and you keep watching backward and you see yourself when you were a little kid. you see yourself as you're being born or see yourself before you're born, you know.
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would you see that? would you see all these things, gang? could you be patient and keep watching time go backward, backward, backward? - answer begins with a... - no. no, you couldn't, okay? the show would be over after this gets to you. it's like if i shake a stick in the water and run out here and wait till the waves come, they don't keep coming forever and ever and ever. it went from the time i started shaking the stick or the time i jumped from here to here? in fact, here's a thing too. everyone take a look at their own hand. put your hand right there. are you guys looking at your hand as it is right now? no, you're all the time looking in the past because light left your hand and it took some time to get to you. so you're seeing your hand as it used to be. you're seeing me as i used to be. i'm seeing you as you used to be. we're all looking at history. now how much? this makes sense when you talk about big distances, big distances. let's suppose you could go faster than the speed of light. come way out and then watch the events on the earth. wouldn't you see them a long time ago, you know?
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let's suppose you got out like 2,000 light years away, 2,000 light years away. right now, boom instantaneously you're out in the universe 2000 light years away from the earth, looking at the earth. what does the calendar say? they say like zero, yeah? all right, of course, they made the calendar and things later on. let's suppose it's like 25 and you see the calendar like you know, b. c., right? you see someone's calendar, and sometimes the calendar might be something like this. hanging on the wall, right, okay? were there ever calendar at the-- come on, how do they know? no, but the point is if could get way, way out there, you could see the earth 2000 years ago. paul? is that same type of theory that you're talking about like the space telescope they're gonna launch on the shuttle,
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it's gonna be able to look back closer towards the big bang than we can now? yes, we're looking in the past, yes, yes. you guys know this, when you look at the stars, you know that stars might not even be there. you know that. and the closest star is what? what's the closest star? it's our favorite. the sun and the sun's 8 light minutes away. it takes 8 minutes for light to get to us. the next nearest star, alpha centauri, looks like a proper star, right? what do you think our star will look like if it gets farther away? what's our star look like from pluto? our sun from pluto looks like all the other stars. but you're looking at them in the past. now anyone out there looking at us right now is looking at us in the past. no one can see us right now and like i said, didn't you have trouble seeing your hand? hey, i'm not sure that was my hand. i'm exaggerating there. but yeah, they have these things, but let me just short circuit things and ask this, gang. let's suppose someone was kind enough to put a mirror
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way out on a planet. and make it so it's pointing right down to us and it's 1,000 light years away. you know what i'm talking about, 1,000 light years? it takes 1,000 years for light to go up there. or it takes 1,000 years for light to go down here. now sometimes you guys in the morning you get up and you brush your teeth, why do you guys look at the mirror when you're brushing your teeth by the way? have you ever noticed that? you brush your teeth, you look in the mirror, yeah? or you're combing your hair, you look in the mirror, right? when you look in the mirror, you see yourself almost at the same time, right? now what if the mirror gets farther away, farther away, farther away? you start to comb your hair and you have to wait a little while. ain't that true? well, let's suppose this mirror is 1,000 light years away and you're over here and you're combing your hair, how long you have to wait to see yourself? 2,000 years. but let's suppose you're not interested in seeing yourself, you're interested in seeing where you came from.
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and you just take a plain old look in the mirror. and you see the earth. you see the earth at what time? you see the earth 2,000 years ago. and if you could really resolve that and get a clear image, you would really see what the earth looks-- never mind the books, never mind the carbon dating, never mind all the records. honey, you just look and you'd see it. now has anyone put a mirror up there for us? haven't found any mirrors yet. but here's some speculation. i wonder maybe just matter in the universe might be able to reflect and the image might be there. maybe in the future, we can do such things. it'd be kinda blurry, but who knows. at this point nothing much surprises me. another effect of relativity of high speeds is the increase in momentum of things,
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but more than the speed would dictate, it appears that the mass itself, the mass of an object itself increases with sed. and we have a relation for that and that relation is this. would you guys like to have a real rush, a real rush? by that i mean, you know, sometimes you go out and you see a sunset and you look at the sunset and the sunset is so beautiful and you're with a friend and you just get this rush. it just feels so good. it is one of those feelings you're glad you're alive, yeah? or you hear the proper music and you say... it just does it to you, right? sometimes something will happen and... would you like to have that experience today in this classroom. and you go home tonight and say, mom and dad, man, i got a rush in class today.
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what that dude did in that board was more beautiful than anything i can remember ever seeing in my life. would you like to see that? would you like to have that kind of a rush, that kind of an emotional high? would you like to have that? i can do it for you right there. i'm gonna give you all the relativity equations in one part of the board, watch this. gaze, gaze. now i know what you guys are feeling, but let me tell you the difference between you guys and other people. if a janitor walked in here the janitor would just look at that and think nothing of it and walk right by. but when you guys look at that, don't you, ah, beautiful. is there anyone here that does not feel that feeling? everybody? only one?
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only two? that do it for you guys, huh? there it is, there's all the relativity right there. it turns out that the mass of things will become more with speed. it turns out when this lorentz factor is down below, it's gonna make the quantity always bigger. this will always be less than 1. so something less than 1 divided by something will make this bigger. so it turns out the time always gets stretched out. the mass always becomes more. but the length of things becomes less and things contract. and when you put these things all together you get the equation of the 20th century, e=mc2, which tells us that that which we call energy and that which we call mass, two sides of the same coin. if you go to stanford, california, you'll see the stanford linear accelerator. you're driving down the freeway 280,
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there's a great big long concrete tube, two miles long. and that concrete two-mile-long tube, they fire electrons. and these electrons go right down a vacuum pipe. gotta get all the air away, they don't want to get these electrons to get obstructed. and they'll fire for two miles down that tube. and when they get to the end, boom, they smatter into particles of matter and they smash it all apart and they take a look to see what it's made of. for example if i wanna know what this watch is made of, the one way to find out what this watch is made of is to take the watch, find a concrete wall, take that watch and throw it as fast as i can. and when it splatters, take some pictures, quick. and that way i can find out what's inside. does that make sense? well, that's what the physic-ers do. they do that with atoms and they smash them apart and they see all the debris. they take photographs and they get it. well, that's what the people do at the stanford linear accelerator. well, it turns out those particles are electrons. the electrons that are shot in your tv tubes, same old electrons. and those electrons are going 99.9999999999999% the speed of light by the time they hit the target at the end,
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honey, they are going fast. but let me tell you something, that was kinda neat. those electrons in the rst couple of feet are going more than 99% the speed of light right there. and they're push all the way down. push, push, push, push, push. the copper wires feeding that accelerator are thicker than your wrist. enormous amperage, enormous power. and that is put into dring that accelerator. and that energy takes little tiny part electrons. you know how light they are, my goodness, my goodness? it pushes, pushes, pushes, pushes for 2 miles. and as they push and push and push and doesn't gain much speed. but it gains something else. it gains momentum without gaining much speed. and what's that imply about the mass? that the mass is becoming enormous. when these things get down the end, they land--they hit with thousands of times more mass than they started with. and so all this energy you're pping in, all that energy, that energy is going into mass.
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and how much? given by this relationship. so at the end of the tube, you'll have more mass than you had when you started. because you're energizing it all the time. and as you push things, push things, some people will say w come you can't go faster than the speed of light? well, to go faster than the speed of light, if you gotta push, you gotta push, you gotta push, when you wanna accelerate something, there are two factors involved. some of you people know what the two factors involved are. if someone said to y, hey, you, you're a physics type, huh? i undersnd that acceleration involves two ideas. what are those ideas? and you would y how hard you push, force, compared to how much inertia you have, mass, isn't that right? so force per mass. now as you're pushing faster and faster and faster and the mass becomes more and more and more, what happens at the speed of light? at the speed of light, what would the mass be? see this little piece of chalk.
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what's the mass of this piece of chalk if i push it to the spe of light? i can use this equation to guide me. if v is the speed of light zero...infinity. this mass will be pushed to the infinite. now someone says, now that it has an infinite mass, which means an infinite resistance to any furth change in motion. now if someone says, could you push it in hyperdrive, honey? hyperdrive, i've got an infinite resistance to any change in motion now. and so we find out in the universe as we understand it in the 20th century, you can't do that. at least with material particles there is a speed limit, the speed of light. so you get that down. one of the important parts of relativity is this. before we understood relativity,
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we understood that the human race, no matter how sophisticated they became couldn't travel very far in space. and the reason is simple enough. the center of our galaxy for example is 20,000 light years away. it takes 20,000 years for light itself to go from the center of our galaxy to us. and our galaxy is nothing compared to the expanse of the whole universe. so how are you gonna be going through the universe when you can't even get to your galaxy, it's not gonna take you 20,000 years. if you're traveling at high, high speed, you might get there in 5 minutes. and if you travel at the speed of light, how far away would it be from a speed of light frame of reference. what's the distance between things. i remember leon russell used to sing that song, "i love you in a place where there's no space and time. i love you forever, you're fend of mine." a place where there's no space and time. that makes sense? how can there be no space.
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how about the speed of light frame of reference. from a speed of light frame of reference, what's the length between one edge of the universe and the other... when v is c? zero. from a speed-of-light frame a reference, there is no distance at all between the one side of the universe and the opposite. and from a speed-of-light frame of reference, how does the duration of time travel? it's frozen: no time, no space. did you ever hear the buddhist type say everything, the universe, really, is just a point in space. you say, gibberish. gibberish? maybe from one frame of reference, that's true. think about that.
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# tvDemocracy NowLINKTV December 4, 2012 8:00am-9:00am PST

News/Business. Independent global news hour featuring news headlines, in depth interviews and investigative reports. (CC) (Stereo)

TOPIC FREQUENCY
Duration 01:00:00
Rating PG
Scanned in San Francisco, CA, USA
Source Comcast Cable
Tuner Channel 89 (615 MHz)
Video Codec mpeg2video
Audio Cocec ac3
Pixel width 544
Pixel height 480